Reduced Vertical Separation Minima (RVSM) requirements dictate substantial improvements in air-data systems and aircraft installation and maintenance. RVSM airspace is any airspace or route between 29,000 ft and 41,000 ft inclusive where aircraft are separated vertically by 1,000 ft (300 m). RVSM decreases the minimum vertical separation from 2000 ft and is being implemented world-wide on a region-by-region basis. Conventionally, minimum vertical separation requirements were 2000 ft and pressure altitude monitoring equipment, which directly measured the pressure outside the aircraft, was used to determine the pressure altitude and provided a proper tolerance to comply with the 2000 ft minimum separation requirement.
With the implementation of RVSM, older pressure altitude measuring equipment and installations may not have sufficient accuracy or reliability to meet RSVM requirements.
RVSM altitude monitoring requirements lead to increase cost for upgrading or replacing conventional air-data equipment. Accordingly, there is a need for a pressure altitude monitoring system that meets RSVM requirements without costly aircraft modifications and testing. Further, there is a need for an algorithm that uses cross compared geometric altitude and temperature to correct errors in pressure altitude measurements. Further, there is a need for a cross compared GPS altitude and temperature based synthetic pressure computation system which provides a synthetic pressure altitude and meets the RVSM requirements. Further, there is a need for the use of a cross compared geometric altitude that is suitably compensated with temperature and wind measurements, to produce a synthetic pressure altitude measurement. There is also a need for a cross compared GPS based synthetic pressure computation system that may be used as an independent monitor in a dual RVSM air-data system to help determine whether an RVSM air-data system is in error.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.
An example of the invention relates to a method of generating a synthetic pressure altitude. The method includes providing a static air temperature to a data processing device. The method also includes receiving a geometric altitude from a geometric altitude sensing device and performing a numerical integration based on the static air temperature and the geometric altitude resulting in a synthetic pressure altitude. The method further includes receiving a pressure altitude from a pressure altitude sensing device, comparing the pressure altitude and the synthetic pressure altitude and generating an average of the pressure altitude and the synthetic pressure altitude. The method still further includes providing selectively, based on the comparing step, the average as output.
Another example of the invention relates to a method of determining the pressure altitude of an aircraft. The method includes providing a static air temperature to a data processing device from a temperature measuring device on the aircraft, receiving a geometric altitude from a geometric altitude sensing device, and performing a numerical integration based on the static air temperature and the geometric altitude to provide a synthetic pressure altitude. The method also includes receiving a pressure altitude from a pressure altitude sensing device, comparing the pressure altitude and the synthetic pressure altitude, and generating an average of the pressure altitude and the synthetic pressure altitude. The method further includes providing selectively, the average as output.
Yet another example of the invention relates to a pressure altitude determining system. The system includes a data processing device. The system also includes an air temperature monitor communicating air temperature data to the data processing device and a geometric altitude monitor communicating geometric altitude data to the data processing device. The data processing device carries out a numerical integration based on the air temperature data, and the geometric altitude data, to generate a synthetic pressure altitude. The synthetic pressure altitude data is generated based on a comparison between a measured pressure altitude and the computed synthetic pressure altitude.
Alternative examples and other exemplary embodiments relate to other features and combination of features as may be generally recited in the claims.